rustでcargo checkしたとき、詳細なwarningがでないとき

cargo checkで詳細なワーニングがでないとき

> cargo check
       Fresh bitonic-sorter v0.1.0 
    Finished dev [unoptimized + debuginfo] target(s) in 0.02s

一度、"cargo clean"してから、 "cargo check"に-vをつけると、詳細なワーニングが表示される。

• ”cargo clean"
• "cargo check -v"

 > cargo clean   
 > cargo check -v
    Checking bitonic-sorter v0.1.0 
     Running `rustc --edition=2018 --crate-name bitonic_sorter src\lib.rs --color always --crate-type lib --emit=dep-info,metadata -C debuginfo=2 -C metadata=1159761d94f87fac -C extra-filename=-1159761d94f87fac --out-dir 
 OUTDIR -C incremental=INC_DIR -L dependency=DEP_DIR
warning: unused variable: `x`
 --> src\first.rs:8:13
  |
8 | pub fn sort(x: &mut [u32], up: bool) {
  |             ^ help: consider prefixing with an underscore: `_x`
  |
  = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `up`
 --> src\first.rs:8:28
  |
8 | pub fn sort(x: &mut [u32], up: bool) {
  |                            ^^ help: consider prefixing with an underscore: `_up`

warning: unused variable: `x`
  --> src\first.rs:13:13
   |
13 | fn sub_sort(x: &mut [u32], up: bool) {
   |             ^ help: consider prefixing with an underscore: `_x`

warning: unused variable: `up`
  --> src\first.rs:13:28
   |
13 | fn sub_sort(x: &mut [u32], up: bool) {
   |                            ^^ help: consider prefixing with an underscore: `_up`

warning: unused variable: `x`
  --> src\first.rs:18:21
   |
18 | fn compare_and_swap(x: &mut [u32], up: bool) {
   |                     ^ help: consider prefixing with an underscore: `_x`

warning: unused variable: `up`
  --> src\first.rs:18:36
   |
18 | fn compare_and_swap(x: &mut [u32], up: bool) {
   |                                    ^^ help: consider prefixing with an underscore: `_up`

warning: function is never used: `sub_sort`
  --> src\first.rs:13:1
   |
13 | fn sub_sort(x: &mut [u32], up: bool) {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[warn(dead_code)]` on by default

warning: function is never used: `compare_and_swap`
  --> src\first.rs:18:1
   |
18 | fn compare_and_swap(x: &mut [u32], up: bool) {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    Finished dev [unoptimized + debuginfo] target(s) in 0.55s